Dust collector devices sometimes use exhaust gas from a valve and pressure tank (reservoir) to back flush filters. Examples of such air filter assemblies are disclosed in, for example, U.S. Pat. Nos. 6,090,173; 4,218,227; 4,395,269; and patent application publication U.S. 2006/0112667 A1, each of these patent documents being incorporated by reference herein.
Proper and effective cleaning of these filters requires that the exhaust jet fill the opening of the filter to be cleaned. In many implementations, the opening of the filter corresponds to the opening in the tubesheet, in which the filter is mounted. This exhaust jet is naturally round and will effectively fill a round opening. The problem of filling a filter opening (or tubesheet opening, in which the filter is mounted) that has any shape other than round has been addressed in the past by placing a device in the direct path of the jet. Placing a jet in this location consumes a portion of the energy of the jet, causes turbulence, increases noise level, and only changes the shape of the jet for a small fraction of the pulse duration. These factors all contribute to poor cleaning effectiveness. Improvements are desirable.